Long-Term Aspirin Use May Reduce Cancer Risk, Study Finds

A large-scale study of more than 600,000 people has shown that long-term aspirin use may significantly reduce the incidence of five types of cancers that affect the digestive system.

The study compared cancer risk between people who had taken aspirin for at least six months (7.7 years on average) with non-aspirin users over a 10-year period. After accounting for a range of factors, the incidence reduction results were significant for five digestive system cancers:

47% reduction in liver and esophageal cancer

34% reduction in pancreatic cancer

24% reduction in colorectal cancer

38% reduction in gastric cancer

Several other cancers outside the digestive system were also assessed, with mixed results. Aspirin use correlated with a reduction in leukemia, lung and prostate cancer incidence, but not with cancers of the breast, kidney or bladder.

While the findings in this study hinge on correlation (not causation), this isn't the first study finding a link between aspirin and lower cancer risk. A number of previous studies found the same link with a reduction in colorectal cancer, culminating in a 2016 report by the US Preventative Services Task Force recommending low-dose aspirin as an effective preventative therapy. A 2016 study also showed that aspirin use may reduce risk of developing bile duct cancer. Conversely, a 2005 Women’s Health Study of 40,000 women found no reduction in overall cancer risk among women 45 and older regularly taking aspirin.

Among its more well-known benefits, low-dose aspirin has been strongly associated with a reduction in cardiovascular disease -- it's been shown to reduce heart attack risk for men 50 and older and women 60 and older.

Long-term aspirin use isn’t without risks of its own, however. As an effective anti-clotting agent (the very reason why it helps prevent heart attacks) aspirin may also increase the risk of internal bleeding, though the incidence is relatively rare.

Why aspirin may reduce cancer risk isn't an easy question, but it could come down to the drug's potent anti-inflammatory properties helping to control the inflammation that fuels the development of several digestive system cancers.

"The findings demonstrate that the long-term use of aspirin can reduce the risk of developing many major cancers," reported lead study author Kelvin Tsoi of the Chinese University of Hong Kong. "What should be noted is the significance of the results for cancers within the digestive tract, where the reductions in cancer incidence were all very substantial, especially for liver and oesophageal cancer."

David DiSalvo is the author of "Brain Changer: How Harnessing Your Brain’s Power to Adapt Can Change Your Life" and the best-selling "What Makes Your Brain Happy and Why You Should Do the Opposite", which has been published in 13 languages. His work has appeared in Scientif...